The present invention relates generally to methods and apparatus for controlling radio frequency (RF) energy output from a portable electronic communication device. More particularly, the invention relates to systems for reducing RF output when the device is in proximity with human tissue.
Electronic devices such as tablets and mobile phones employ proximity sensing (p-sensor) antennas to transmit and receive RF power. When a typical p-sensor antenna detects proximity to an object with a high dielectric constant, a control circuit within the device interprets that detected proximity as presence of human tissue. RF power is then reduced to a level that is in compliance with regulatory requirements.
Unfortunately, conventional p-sensor antennas cannot distinguish between human tissue and other high dielectric objects like a desk or a book. Thus a device with a conventional p-sensor antenna enters dynamic power reduction (DPR) mode with detection of any high dielectric object. For example, putting the device on the desk or metallic surface will keep the DPR function running with low RF power. This often causes network disconnection and low throughput issues.
As can be seen, there is a need for an electronic communications device that may reduce RF power output only when in proximity to human tissue. More particularly, there is a need for an antenna system for such a device which is capable of distinguishing between proximity to an inanimate object and proximity to human tissue.